Patches, used in arrays as microwave or millimeter wave power radiators, are a well established method of achieving planar, that is, thin, printed circuit antennas. Such antennas have been two-dimensional, that is, they have used one surface of an insulative substrate as the array of patches and the other surface as the required ground plane.
This requires that for multiple polarization arrays, the patches be fed and radiate both polarizations simultaneously, and little success has been achieved in doing this. Multiple frequency or multiple beam arrays are virtually impossible.